The term product stack refers, in particular, to a plurality of packaging types, packages, bags, or the like that are preferably combined or stacked to create a rectangular product stack. The stack is typically formed on a pallet, but it is in principle also possible to apply the inventive method to a product stack without a pallet. Furthermore, the object being wrapped according to the invention can be a product stack formed of only a few stacked items, or even an individual larger item, such as, for example, those from the white goods sector (washing machines, refrigerators, dishwashers, and the like). The scope of the invention furthermore comprises the fact that the film is of plastic, and preferably a shrinkwrap film composed of plastic that can be shrunk onto the product stack under the action of heat. This enables the item(s) in the product stack to be held tightly together, and, in particular, secured against slipping out of position or the like.
A variety of such wrapping methods are known in practice. Based on their various loading formats for the product stack, the paper industry, for example, wraps packages as follows. A film cover sheet is first placed on the top of the product stack so as to project by 100 mm to around 300 mm down below the horizontal upper surface of the product stack. A film strip is then wrapped around the vertical sides of the product stack, which strip encloses the projecting film segments of the film cover sheet. An edge of the film strip typically projects 50 mm to 400 mm wide beyond the top face of the product stack. A following step then involves welding the upwardly projecting edge of the film strip down onto the film cover sheet. In another known procedural approach, the film strip is first placed around the product stack, the outwardly projecting edges are folded down over the top face of the product stack and secured there. The film cover sheet is then applied and welded in a further step to the folded-in edges of the film strip.
Both of the above-described procedures have disadvantages. The folded-in edges of the film strip are folded in three layers, in particular, at the corners of the product stack and can thus be heated only slowly and incompletely during the welding process. This creates unsealed folds and capillaries, with the result that water can get under the film cover sheet from the side. Paper products especially can become covered with mold as a result. In addition, air can also be trapped between the film cover sheet and the folded-in edges of the film strip, thereby allowing bubbles to form that can tear open during the stacking action and enable water to enter.